1. Field of the Invention.
This invention relates to oil wells and more particularly to pressure relief valves in the eduction tube used for removal of paraffin from existing oil wells.
2. Description of the Prior Art.
A problem exists in producing oil from certain formations with the paraffin coating out on the inside of the eduction tube. Normally, the oil in the producing formation is at an elevated temperature so the paraffin within the crude oil is melted. As the petroleum is brought to the surface, the oil cools and the paraffin precipitates out, normally upon the side of the eduction tube causing a problem. Therefore, the bottom portion of the eduction tube will normally be clear of precipitated paraffin, but the upper portion will have paraffin therein.
It has been known for some time that a pressure relief valve could be placed in the eduction tube below the point where the paraffin is formed and heated oil pumped into the eduction tube from the surface to clear the paraffin out. Such a method with equipment is shown in DANA, U.S. Pat. No. 2,300,348. Instead of using heated oil, different solvents could be pumped in from the surface to dissolve the paraffin.
Problems exist when pulling the eduction tube (or ramming it into the well) with projections projecting from the well. Therefore, various sturdy tools are necessary. Sometime large sections are used, e.g., WALDRON, U.S. Pat. No. 3,361,205.
Cupped or Belville washers were known before this invention.
At the time of filling this application, applicant was aware of the following U.S. patents: Abbott U.S. Pat. No. 3,152,645; Grounds U.S. Pat. No. 3,102,590; Weaver U.S. Pat. No. 3,014,531; Henderson U.S. Pat. No. 3,085,629; Tomlin U.S. Pat. No. 3,376,936; Dana U.S. Pat. No. 2,415,729; Deerdoff U.S. Pat. No. 2,770,307; Willigen U.S. Pat. No. 2,704,979; Hubbard U.S. Pat. No. 3,169,587;